From Intraoperative Angiography to Advanced Intraoperative Imaging: The Geneva Experience

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1 From Intraoperative Angiography to Advanced Intraoperative Imaging: The Geneva Experience Karl Schaller, Marc Kotowski, Vitor Pereira, Daniel Rüfenacht, and Philippe Bijlenga Abstract Objective: We aimed at the integration of recent flat panel technology in a joint interventional suite for neurosurgeons and neuroradiologists. Methods: A Flat Panel system, allowing for intraoperative performance of 2D and 3D DSA, for automated segmentation of vascular structures, and for performance of computed tomography, was connected with a surgical microscope and neuronavigation. All surgical and neurointerventional cases were monitored and stored in a prospective data base. Results: N¼99 patients were treated neurosurgically: N¼63 aneurysm clippings in n¼51 patients; n¼12 resections of arteriovenous malformations (AVM); n¼6 clippings/excisions of dural AV fistulae (davf); n¼3 EC-IC bypass procedures; n¼10 resections of skull base tumours; n¼17 spine procedures. All patients had intraoperative imaging for angiographic control and/or for anatomical allocation. Intraoperative 3D-rotational angiography was performed n¼54 times in n¼42 patients in <15 min each, with repositioning of aneurysm clips in n¼9 patients. Conclusion: This hybrid neuro-interventional suite opens a new avenue for intraoperative imaging by the provision of highly resoluted angiographic or CT images, which may be co-registered with a navigation system. In addition, the workflow in treatment of aneurysmal SAH can be improved, as all diagnostic and therapeutic measures can be taken without having to move the patient to other facilities. K. Schaller (*), M. Kotowski, V. Pereira, D. Rüfenacht, and P. Bijlenga University of Geneva Medical Center, Faculty of Medicine, University of Geneva, Rue Gabrielle-Perret Gentil 4, 1211 Geneva, Switzerland karl.schaller@hcuge.ch Keywords Flat panel Intraoperative angiography Intraoperative CT Intraoperative imaging Vascular neurosurgery Introduction Neurosurgeons deal with intracranial and spinal vascular, bony, and soft tissue pathologies, or with a combination of those. Due to its strength for the visualization of soft-tissue properties, intraoperative MRI (iomri) has become an important tool for resection control in surgery of intra-axial brain tumours, and in pituitary surgery [1]. It requires large and expensive equipment, however, and its use is still not very intuitive in a strictly surgical sense. Intraoperative CT (ioct) scanning requires large equipment as well, and interferes with the natural course of surgery as the patient needs to be moved into the gantry [2]. Furthermore, vascular imaging does not allow for dynamic visualization of blood flow. Recent Flat Panel (FP) technology allows for imaging of vascular structures at high spatial and temporal resolution with up to 100 images/s. In addition, it allows for bone imaging at high spatial resolution, e.g. precise visualization of the human skull base, or of trabecular bone of the human spine. The hardware itself is smaller than previously used X-ray machines, and it can be ceiling-mounted, or attached to robotic arms. This technology may represent an interesting alternative to the above-mentioned modalities, iomri and ioct due to its flexibility and due to the fact that it allows for dynamic vascular imaging, as well as for flat panel derived computed tomography as well. In addition, adaptation of image-guidance could allow for co-registration of the various image modalities taking advantage of each of those. It was our ambition to develop and to evaluate a joint hybrid neuroradiological and neurosurgical interventional suite, based on FP technology (Figs. 1 3). M.N. Pamir et al. (eds.), Intraoperative Imaging, Acta Neurochirurgica Supplementum, Vol. 109, DOI / _18, # Springer-Verlag/Wien

2 112 K. Schaller et al. Materials and Methods Infrastructure Fig. 1 Illustration of basic setup in the hybrid room. The Flat Panel system, including table with radiolucent headholder, and overhead monitors. Not in the figure: Surgical microscope and neuronavigation, which are coupled with the FP system. 3D screen and Neuromonitoring system The hybrid interventional room is located between diagnostic radiological facilities, such as MRIs, the emergency surgical suites of the hospital, and the urological operating rooms. It can be entered from three sides. The assigned interventional room surface was restricted to 65 m 2 for local architectural reasons. In addition, there is a control room with all monitors and computer workstations, shielded by protecting glass towards the interventional suite, and a small storage room with a scrubbing facility adding to another 25 m 2. Local bioengineers have evaluated the hygienical aspects, as the room was intended for use in diagnostic and in open surgical interventions. Therefore, a vertical laminar air flow system had to be installed at the foot end of the interventional table. Fig. 2 Example of joint neurosurgical neuroradiological intervention. Sixty-eight-year old woman with incidentally found aneurysms of her right superior cerebellar (SCA) (a), anterior communicating (Acom) (b), left middle cerebral (MCA) (c), and left posterior communicating (Pcom) (c) arteries. All aneurysms were treated the same day, on the same table, during the same session. Interventional neuroradiologists started with coil occlusion of the right SCA aneurysm. These images underscore the quality of the 3D angiographic images

3 From Intraoperative Angiography to Advanced Intraoperative Imaging: The Geneva Experience 113 Fig. 3 Intra-operative angiographic control, showing complete occlusion of all aneurysms (2D DSA) in anterior posterior (a) and lateral (b) view. Please note the limited artefacts of the headholder Equipment A monoplane Philips Allura FD20 system (620 projections along 240 in 8 10 s, rotational speed: 30 /55 /s, 30 frames/s), allowing for automated segmentation of vascular structures was installed (Philips Medical systems, Best, Netherlands). This system allows for dynamic imaging (e.g. angiography), as well as for CT imaging. The accompanying (angio-)table can be adjusted in height only in its present version. A special adapter for the radiolucent head clamp (Doro, Promedics, Düsseldorf, Germany) was constructed. A BrainLAB neuronavigation system (VV 2 ; BrainLAB, Heimstetten, Germany) was installed in addition, and a recent surgical microscope (Zeiss Pentero; Zeiss, Oberkochen, Germany) including an Indocyanine green (ICG) videoangiography unit completed the basic equipment. The microscope is navigable, and the navigation system was adapted for integration and co-registration of FP-derived images (angiography and CT) with conventional imaging data sets. All surgical and neuroradiological and joint interventions were prospectively stored in a data base. All patients had intra-operative imaging for anatomical allocation (e.g. FP CT scanning for resection control in skull base tumours) or for angiographic control (e.g. of clipped aneurysms). Co-registration of intraoperatively acquired imaging data (either angiographic, or FP CT) with the navigation system was performed when considered useful for the intervention. Results Open Neurosurgical Patients A total of n¼99 patients were treated neurosurgically within a 19-month period of time (February 2008 September 2009). This includes n¼63 aneurysm clippings in n¼51 patients, n¼12 resections of arteriovenous malformations (AVMs), n¼6 clippings/excisions of dural AV fistulae (davf), n¼3 EC-IC bypass procedures, n¼10 resections of skull base tumours, and n¼17 complex spine procedures. Intraoperative 3D-rotational angiography was performed in all vascular patients in <15 min each. It allowed for direct control of aneurysm-clipping and displayed incomplete clipping (n¼7) or vascular compromise (n¼2). Direct repositioning of aneurysm clips was performed in n¼9 patients. Thereby, intraoperative 3D angiography had stipulated clip correction in 14.3% of aneurysms, thus allowing complete aneurysm occlusion in 100%. Intraoperative FP-based CT scanning was performed in skull base tumours. It was particularly helpful, where a far lateral transcondylar approach had to be used in a recurrent foramen magnum meningioma, and in a partially calcified clival chordoma (see Figs. 4 and 5). The respective intraoperative data sets were co-registered with preoperative images on the navigation system. However, soft tissue properties could not be visualised with the same quality as with extraoperative CT and certainly not as with MRI. Two patients of the whole series developed locally confined decubitus following prolonged lateral positioning. Neuroradiological Patients Within the same period, a total of n¼147 diagnostic and n¼106 interventional (neuroradiological) procedures were performed (n¼51 coilings, n¼28 stentings, n¼13 AVM- or AVF-embolizations, n¼14 vertebroplasties). In addition, n¼364 percutaneous infiltrations were performed. Discussion In the same way, neurosurgeons are eager to perform resection control in case of intrinsic brain tumours by intraoperative MRI, they are looking for innovative ways of

4 114 K. Schaller et al. Fig. 4 Intra-operative 3D skull radiography during extended far lateral approach for a skull base tumour. These images can be transferred and co-registered with the navigation station intraoperative visualization in neurovascular surgery, in surgery around the skull base, and for spine surgery. That goal should be accomplished in an intuitive manner, and whatever methodology applied it should not interfere too much with the surgical workflow. As the physical properties of the tissues neurosurgeons are dealing with are so different from each other, it is very unlikely to achieve this goal with a single imaging modality in the near future. As far as it concerns vascular imaging, the dynamics of intravascular flow have to be considered in addition. Whereas iomri is steadily advancing, e.g. in the field of glioma and pituitary surgery, there have not been reasonable approaches for vascular and skull base surgery so far [1, 3, 4]. Spatial resolution and lack of practicability of conventional angiographic tools did not promote their application in a surgical environment, despite the clear advantage of e.g. having the opportunity to perform direct control of surgical clipping in cerebral aneurysm surgery [5, 6]. Thus, some surgical groups perform direct post-operative angiographic control with the patients still anesthetized, in order to take them back to surgery directly in case of incomplete aneurysm clipping or inadvertent clipping of a parent vessel [7]. Indocyanine green videoangiography has become a very important tool in microneurosurgical routine [8]. Its particular value concerns the visualisation of small and perforating vessels, whereas vessels, which are not directly visible though the microscope may escape microangiographic analysis [8]. It should be seen as an excellent complementary tool to advanced intraoperative 3D DSA as this is possible with our proposed concept for integration of FP technology in a hybrid operating room. Another approach is the use of intra-operative CT scanners, the most recent of which do even allow for intraoperative performance of angio-ct scanning in addition [9]. These scanners are large, however, fairly static, and it thus seems reasonable to combine the technical and physical flexibility of recent Flat Panel technology in order to overcome the shortcomings of standard 2D DSA and CT scanning. Whereas the direct advantage of such a hybrid interventional environment may not be as obvious for surgery of intracranial tumours, it has to be stated that the integration of such a joint neurosurgical neuroradiological suite may change and improve the overall in-house management and workflow of neurovascular emergencies: E.g., currently, one has to transfer a patient with acute SAH from the emergency department to the CT scanner, then to the ICU, or to the OR for placement of an external drainage, then to the angiography suite for further diagnostics, and finally totheoperatingroom,iffreeatthetime.control angiography has to be scheduled separately in the conventional setup. The proposed hybrid concept allows for completion of all diagnostic and interventional/surgical activities, including CT, DSA, and open, or endovascular aneurysm treatment plus immediate control of aneurysm occlusion. All can be done in the same room, on the same table, and even jointly (e.g. preparation for arteriography and placement of external ventricular drainage). Unfortunately, two patients developed locoregional and reversible decubitus after having been placed in the lateral position for several hours. It is quite clear that the present solution with a modern yet standard angiography table is not sufficient for use in an important number of neurosur-

5 From Intraoperative Angiography to Advanced Intraoperative Imaging: The Geneva Experience 115 Fig. 5 Intra-operative CT-images, obtained with Flat Panel system, for resection control in case of large calcified clival chordoma, which was approached via the sublabial transsphenoidal route. Remnants of the calcified tumour can still be appreciated on axial images (a), as well as inferiorly on sagittal reconstructions (b) gical pathologies. The next evolutionary step of such a hybrid room should concern the development of a specifically adapted carbon table, which can be adjusted like any other operating table. Conclusion The new neuro-interventional suite opens a new avenue for intraoperative imaging by the provision of highly resoluted CT or angiographic images, which may be co-registered with a commercially available navigation system. High temporal resolution of vascular diagnostics may assist in developing better virtual and customized treatment plans for patients suffering from aneurysms and vascular malformations. In addition, the workflow in treatment of aneurysmal subarachnoid hemorrhage can be improved significantly, as all diagnostic and therapeutic measures can be taken without having to move the patient to other facilities. In addition, due to high resolution of bony structures and the connection with image guidance, there is good potential concerning skull base and spinal surgery. The further development of a fully-functioning carbon-made surgical table is recommended. Conflicts of interest statement The project to develop this experimental joint interventional suite benefitted from the following: Brain- LAB supported the project by the one-year cost-free use of a navigational system and Philips Medical Systems provided regular cost-free upgrades of software. References 1. Nimsky C, von Keller B, Schlaffer S, Kuhnt D, Weigel D, Ganslandt O, Buchfelder M (2009) Updating navigation with intraoperative imaging data. Top Magn Reson Imaging 19: Matula C, Rössler K, Reddy M, Schindler E, Koos WT (1998) Intraoperative computed tomography guided neuronavigation: concepts, efficiency, and work flow. Comput Aided Surg 3: Gerlach R, du Mesnil de Rochemont R, Gasser T, Marquardt G, Reusch J, Imoehl L, Seifert V (2008) Feasibility of Polestar N20, an ultra-low-field intraoperative magnetic resonance imaging system in resection control of pituitary macroadenomas: lessons learned from the first 40 cases. Neurosurgery 63: Jankovski A, Francotte F, Vaz G, Fomekong E, Duprez T, Van Boven M, Docquier MA, Hermoye L, Cosnard G, Raftopoulos C (2008) Intraoperative magnetic resonance imaging at 3-T using a dual independent operating room-magnetic resonance imaging suite: development, feasibility, safety, and preliminary experience. Neurosurgery 63: Alexander TD, Macdonald RL, Weir B, Kowalczuk A (1996) Intraoperative angiography in cerebral aneurysm surgery: a perspective study of 100 craniotomies. Neurosurgery 39: Raabe A, Beck J, Rohde S, Berkefeld J, Seifert V (2006) Threedimensional rotational angiography guidance for aneurysm surgery. J Neurosurg 105: Meyer B, Urbach H, Schaller C, Baslam M, Nordblom J, Schramm J (2004) Immediate postoperative angiography after aneurysm clipping implications for quality control and further guidance of management. Zentralbl Neurochir 65: De Oliveira JG, Beck J, Seifert V, Teixeira MJ, Raabe A (2007) Assessment of flow in perforating arteries during intracranial aneurysm surgery using intraoperative near-infrared indocyanine green videoangiography. Neurosurgery 61(3 Suppl): Uhl E, Zausinger S, Morhard D, Heigl T, Scheder B, Rachinger W, Schichor C, Tonn J (2009) Intraoperative computed tomography with integrated navigation system in a multidisciplinary operating suite. Neurosurgery 64(5 Suppl 2):